Constant velocity universal joints are well known in the art and are employed where transmission of a constant velocity rotary motion is desired or required. The tripod joint is characterized by a bell-shaped outer race (housing) disposed around an inner race.
One common type of constant velocity universal joint is a fixed or Rzeppa style. Fixed constant velocity joints are generally grease lubricated for life and sealed by an elastomeric sealing boot when used on some drive shafts. Most constant velocity universal joints are sealed in order to retain grease inside the joint while keeping contaminants and foreign matter, such as dirt and water, out of the joint. In order to achieve this protection, the constant velocity joint is usually enclosed at the open end of the outer race by a sealing boot made of rubber, thermoplastic or urethane. Such sealing and protection of the constant velocity joint is necessary because, once the inner chamber of the outer joint is partially-filled and thus lubricated, it is generally lubricated for life.
It is often necessary to vent the constant velocity joint in order to minimize air pressure fluctuations due to expansion and contraction of the air within the joint during operation of the joint. Further, in some circumstances the constant velocity joint boot may "blow out" or rupture during high speed operation. Venting is required when using a rubber material for the boot.
U.S. Pat. No. 4,319,467 issued to Hegler et al. discloses a seal vent subassembly press fitted into the collar bore of a universal joint. The subassembly includes a vent disc which is nested in a seal disc to form a venting arrangement to the exterior of the housing by way of various holes and chambers. However, this vent hole may still be subject to grease buildup during a static state or operative state.
U.S. Pat. No. 6,010,409, issued to GKN Automotive, Inc. discloses a vent regulator device adapted for use in a constant velocity joint including a housing having an inner surface defining an inner cavity. The inner surface includes an annular portion, and a domed portion which has a relatively small vent hole centrally located therein. The vent regulator device further includes a member having a first end and a second end where the first end is mounted to the inner surface of the housing and the second end is disposed proximate the vent hole. When the constant velocity joint is in one of either a static state and an active state rotating at speeds below a predetermined threshold, the vent hole is overlappingly covered by the first end of the member, thereby preventing grease from penetrating the hole. Moreover, when the constant velocity joint is in an active state rotating at speeds above the predetermined threshold, centrifugal forces cause the second end of the member to move away radially from the vent hole to allow venting of air therethrough.
Consequently, an improved constant velocity joint design is provided which allows for reliable venting of the joint when large quantities of grease are contained therein. In addition, the design should eliminate grease flow out of the joint and not allow any foreign matter into the joint.